In an unusual move, the Federal Trade Commission confirmed on Thursday that it has opened a probe into the Equifax debacle, which may have compromised the personal information of as many as 143 million Americans.

"The FTC typically does not comment on ongoing investigations," Peter Kaplan, the FTC's acting director of public affairs, said in a statement. "However, in light of the intense public interest and the potential impact of this matter, I can confirm that FTC staff is investigating the Equifax data breach."

Reps for Equifax did not immediately respond to a request for comment.

The company's stock dropped another 8% in early trading Thursday following the FTC statement. The stock fell 15% on Wednesday on investor concerns of an impending investigation.

The confirmation comes one day after Sen. Mark Warner sent a detailed letter to the acting head of the FTC calling for an investigation into Equifax's handling of the breach.

In particular, Warren called for the agency to scrutinize Equifax for potential security lapses and its poor handling of customer service after the breach was disclosed.

Earlier this week, a bipartisan group of dozens of senators also sent a letter urging the FTC, Department of Justice and the Securities and Exchange Commission to investigate Equifax over its executives' stock sales.

Three Equifax executives sold shares of the credit-reporting firm worth nearly $2 million shortly after the breach was discovered. The sales came before the breach was announced to the public.

Equifax may not be the largest data breach ever in terms of the number of people affected, but it may be more significant because of the sensitive information at risk: social security numbers, addresses and the numbers of some driver's licenses.

Maura Healey, the attorney general of Massachusetts, said this week she intends to file the first state lawsuit against Equifax over the breach.

Jeb Hensarling, a Republican Congressman from Texas and the chairman of the House Financial Services Committee, said last Friday that preparations are already underway for a congressional hearing on the matter.